Invalid hook call

똑같이 따라한것 같은데 .. 왜 이런 에러가 뜨는지 모르겠어요..

const React = require('React');
const { useState, useRef } = React;

const Gugudan = () =>{

    const[ firstNum, setFirstNum ] = useState( Math.ceil(Math.random()*9 )  );
    const[ secondNum, setSecondNum ] = useState( Math.ceil(Math.random()*9 )  );
    const[ value, setValue ] = useState('');
    const[ result, setResult ] = useState(''); 
    const inputRef = useRef(null);

    const guguCheck = (e) =>{
        e.preventDefault();

        if( parseInt(value) === firstNum*secondNum){
           
            setResult( `  : correct` );
            setFirstNum( Math.ceil( Math.random() * 9) );
            setSecondNum( Math.ceil( Math.random() * 9) );
            setValue('');
                        
            inputRef.current.focus();
        }else{
            
            setResult('try again');
            setValue('');
            inputRef.current.focus();
        }
    }

    const inputChange = (e) =>{
        setValue(e.target.value);
    }

    

    return (
        <>
            <p>{firstNum}곱하기 {secondNum}는?</p>
            <form onSubmit={ guguCheck }> 
                <input   ref={ inputRef }  type="number" value={value} 
                    onChange={ inputChange } />
            </form>
            <p>{result}</p>
        </> 
    );
}
module.exports = Gugudan;

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